1. Field of the Invention
The present invention relates to a fuel injection controller for supplying an appropriate amount of fuel to an internal combustion engine via an injector, and to an internal combustion engine including the same. More particularly, the present invention relates a fuel injection controller which brings the fuel injection amount closer to the ideal one, and to an internal combustion engine including the same.
2. Description of the Background Art
An internal combustion engine obtains energy by igniting a gaseous mixture of fuel and air with spark plugs, and therefore must maintain the air-fuel ratio of the gaseous mixture properly. Various approaches have been proposed to determine the amount of fuel injected relative to air in a fuel-injected internal combustion engine, for example, see Japanese Patent Laid-Open No. 2003-106203, specifically FIGS. 8 and 11 thereof.
In FIG. 8 of the Japanese Patent Laid-Open No. 2003-106203, an injection instruction signal Vj shown in (B) is issued based on a pulser output shown in (A), thus allowing fuel to be injected.
During this period, a throttle opening θ changes as shown in (C).
PBmap shown in (D) is a map-searched value of intake pressure found for an engine rotary speed and a throttle opening as described in lines 5 to 7 of paragraph [0142] in the Japanese Patent Laid-Open No. 2003-106203
The value PBmap searched immediately prior to the previous synchronous injection time is used as a comparative reference value PBmap0 shown in (E) as described in lines 10 to 12 of paragraph [0142] in the Japanese Patent Laid-Open No. 2003-106203
Then, in FIG. 11 of the Japanese Patent Laid-Open No. 2003-106203, Ti shown in (A) is an actual injection time that begins at time t1. The actual injection time Ti is calculated from a reference injection time Ti0 and a correction amount Tacc.
The correction amount Tacc is determined based on a map-searched value ΔPBmap1 shown in (B). It should be noted that ΔPBmap1 is calculated as ΔPBmap1=(PBmap1−PBmap0).
In other words, the Japanese Patent Laid-Open No. 2003-106203 discloses an approach for calculating a basic injection amount and correcting the basic injection amount in order to specify a synchronous injection amount used to inject fuel in synchronism with a time around the start of an intake stroke. The approach calculates a basic injection amount based on the engine rotary speed at the time of synchronous injection and the intake volume estimated from the intake pipe vacuum pressure in the previous intake stroke. The approach corrects the basic injection amount to compensate for the change in engine load that occurs from the intake stroke of the previous cycle to the synchronous injection of the current cycle. The basic injection amount is corrected based on the difference between two load parameters, one calculated from the throttle opening at the previous synchronous injection and the other calculated from the throttle opening at the current synchronous injection.
As is apparent from the above description given in relation to FIG. 8 of the Japanese Patent Laid-Open No. 2003-106203, PBmap0 shown in (B) of FIG. 11 is a searched value at time t0. As shown in (C) of FIG. 11, the throttle opening is highly likely to change during a period from time t0 to time t1.
In other words, the change in throttle opening in the intake stroke is reflected as a change in intake pressure. Therefore, using the change in throttle opening from before the intake stroke for calculating a correction factor for the basic injection amount as in the Japanese Patent Laid-Open No. 2003-106203, leads to redundantly adding two variations (both variations), a variation in throttle opening and a variation in intake pressure resulting from the change in throttle opening. This makes it likely that the correction will deviate from an ideal one. As a result, it is necessary to fully consider the variation in intake pressure in order to establish a calculation formula and a map for the correction amount, resulting in greater likelihood of complexity and more man-hours needed for experiments.
Against the backdrop of quest for engines with higher performance, a fuel injection controller is desired which can bring the fuel injection amount closer to the ideal one.
The present invention has been made to overcome such drawbacks of the existing fuel injection controller. Accordingly, it is one of the objects of the present invention to provide a fuel injection controller which is capable of bringing the fuel injection amount closer to the ideal one.